The present invention relates to (1) a novel glycidyl sulfonamide compound which is a liquid compound having a low viscosity and which provides a cured material having excellent flexibility and elongation, and more particularly to a glycidyl sulfonamide compound having siloxane or polysiloxane (hereinafter referred to as "(poly)siloxane") main chain in its molecule, and a process for preparing the same, (2) an epoxy resin composition comprising the glycidyl sulfonamide compound which provides a cured material having high thermal resistance and excellent toughness, and (3) a cured material prepared by curing the composition, and more particularly to an epoxy resin composition for epoxy paints which provides a coating film being excellent in flexibility and surface properties and a coating film formed by curing the composition.
Epoxy resins have been widely used for various purposes such as resins for paints, materials for electric apparatuses, adhesive agents, coating materials, materials used in civil engineering and construction industry and matrix materials for FRP because the epoxy resins have excellent properties such as thermal resistance, chemical resistance, adhesive properties and electrical insulating property. Especially, among the epoxy resins, an epoxy resin having at least one N,N-diglycidylamino group in its molecule (hereinafter referred to as "glycidylamine epoxy resin"), an epoxy resin which is prepared by means of a condensation reaction of a bisphenol with an epihalohydrin (hereinafter referred to as "epi-bis type epoxy resin"), and the like are used as adhesive agents having thermal resistance and matrix materials for prepreg used in spacecraft and aircraft since the cured materials prepared by curing with heat the epoxy resins together with curing agents exhibit both high thermal resistance and excellent adhesive property for a substrate.
However, generally, the cured epoxy resin does not have sufficient flexibility, toughness, impact strength, and the like, and does not sufficiently satisfy the mechanical properties required in various uses. Especially, a coating film of the epoxy resin does not sufficiently satisfy the mechanical properties required for paints.
In order to improve the mechanical properties of the epoxy resin such as flexibility and elongation, many attempts such as adding a flexibilizer to usual epoxy resin compositions in order to decrease the stress of the cured material prepared from the resin compositions and adding a filler to the compositions have been made.
Examples of the flexibilizer are, for instance, glycidyl compound prepared from oxyalkylene or polyoxyalkylene such as butanediol diglycidyl ether, glycerol triglycidyl ether, trimethylolpropane triglycidyl ether, polypropylene glycol diglycidyl ether (available from ASAHI DENKA KOGYO K. K. under the trade name of "ED-506", DAINIPPON INK AND CHEMICALS, INC. under the trade name of "Epiclon 707", and the like), polyethylene glycol diglycidyl ether (available from Nippon Oil and Fats Co., Ltd. under the trade name of "Epiol E-100"). These flexibilizers are used as reactive diluents. However, these flexibilizers have the defects that the amount of the flexibilizers should be adjusted to 5 to 20 parts by weight (hereinafter referred "parts by weight" to as "parts") because the properties of the epoxy resin by adding flexibilizers cannot be sufficiently exhibited when the amount is without the range of 5 to 20 parts. Accordingly, the thermal resistance of the cured material of the resin is considerably decreased.
Further, these glycidyl compounds prepared from alkylene ether or polyalkylene ether have the defects that when these compounds are co-cured with an epoxy resin, the obtained cured materials or coating films exhibit a deteriorated thermal resistance and chemical resistance, or an higher water absorption since these compounds have an ether linkage in the main chain of its molecule.
On the other hand, it is known that (poly)siloxane is remarkably excellent in thermal resistance, weatherability and oxidation deterioration resistance compared with (poly)ether because Si--O linkage has larger bonding energy than C--O linkage. The (poly)siloxane which is well-known as silicon oil is also excellent in water repellency, hydrophobic property and electric property, while the (poly)ether exhibits water absorption. The (poly)siloxanes are widely used as heating medium, lubricating oil, and the like because the (poly)siloxanes have the above properties. For instance, a process in which a silicone rubber having a good stability against oxidation is blended or dispersed into an epoxy resin is proposed (Japanese Unexamined Patent Publication No. 21417/1983). However, it is known that (poly)siloxane has a defect that the (poly)siloxane is bled on the surface of the cured resin due to thermal history when the (poly)siloxane is merely blended and dispersed into an epoxy resin since (poly)siloxane is essentially poor in compatibility with as epoxy resin (Japanese Unexamined Patent Publication No. 116654/1987).
A process in which various rubber modifiers such as carboxyl group terminated butadiene-acrylonitrile rubber (CTBN) and amino group terminated butadiene-acrylonitrile rubber (ATBN) are added into an epoxy resin to form a cured material of which structure is like seas and islands in order to control the thermal resistance of the cured epoxy resin, is also proposed (refer to "Shin-epokishi-jushi" (new epoxy resin) edited by Hiroshi Kakiuchi and published by Shoko-do, and the like). These rubber modifiers, however, have a defect that long-term heat resistance of the cured material of the resin containing the modifiers is deteriorated because the rubber modifiers are very poor in oxidation resistance.
From the viewpoints mentioned above, a novel flexibilizer which imparts flexibility to cured materials or coating films of the epoxy resin without deteriorating the properties of the cured material or coating film of the resin, particularly, without increasing the water absorption, has been desired.
An object of the present invention is to provide a glycidyl compound which can be co-cured with an epoxy resin to give a cured material or a coating film having excellent toughness, flexibility and elongation, without largely deteriorating the thermal resistance of the cured epoxy resin.
These and other objects of the invention will be apparent to one skilled in the art upon consideration of the following description and appended claims.